xchat python should have constants defined for event names

[Chad Miller]

Binary package hint: xchat-gnome

In the xchat Python API, we need to know event names, but these are defined nowhere and documented nowhere.

We are expected to hook to events using something like

xchat.hook_print(event_name_string, function_callback)

but the contents of 'event_name_string' are nowhere defined. It's only by looking in the unrelated 'xchat' program's preferences that we have an idea of what could go there.

Instead, the xchat module should define EV_CH_MSG and EV_CH_MSG_HIGHLIGHT and EV_MSG_FROM_YOU and all others so that we are able to write
xchat.hook_print(xchat.EV_CH_MSG, function_callback)
instead of
xchat.hook_print("Channel Message", function_callback)
, and so that we have a reference to know what events are supported.